diff --git a/Parser.js b/Parser.js
index 1c7ef633..ff479870 100644
--- a/Parser.js
+++ b/Parser.js
@@ -271,6 +271,7 @@ var copyFuncs = {
     "rel": [
         "rel",
         "\\approx",
+        "\\cong",
         "\\ge",
         "\\geq",
         "\\gets",
@@ -360,7 +361,7 @@ Parser.prototype.parseNucleus = function(pos) {
                 "Expected group after '" + nucleus.text + "'");
         }
     } else if (utils.contains(sizeFuncs, nucleus.type)) {
-        // If this is a color function, parse its argument and return
+        // If this is a size function, parse its argument and return
         var group = this.parseGroup(nucleus.position);
         if (group) {
             return new ParseResult(
diff --git a/buildTree.js b/buildTree.js
index 167b4936..42d9587b 100644
--- a/buildTree.js
+++ b/buildTree.js
@@ -423,6 +423,7 @@ var charLookup = {
     "\\cdot": "\u22c5",
     "\\circ": "\u2218",
     "\\colon": ":",
+    "\\cong": "\u2245",
     "\\div": "\u00f7",
     "\\ge": "\u2265",
     "\\geq": "\u2265",
diff --git a/test/katex-tests.js b/test/katex-tests.js
index e8caa910..f7343b2e 100644
--- a/test/katex-tests.js
+++ b/test/katex-tests.js
@@ -63,7 +63,7 @@ describe("A bin parser", function() {
 });
 
 describe("A rel parser", function() {
-    var expression = "=<>\\leq\\geq\\neq\\nleq\\ngeq";
+    var expression = "=<>\\leq\\geq\\neq\\nleq\\ngeq\\cong";
 
     it("should not fail", function() {
         expect(function() {